Looked at your code and saw it was far more complicated then is seems it needs to be.

WorldMapBossButtonFrame:SetAlpha(0)
or
WorldMapBossButtonFrame:Hide()

should be all you need.

Maybe I am not seeing the necessity in doing anything with the digsites or quest objectives.

Edit: I see now that those lines of code are to determine proper placement of the checkbox. You could still simplify the hiding code to just hide the entire frame the buttons sit on, instead of hiding the buttons individually.